FILE PHOTO - Mick Roelandts, firearms reform project manager for the New South Wales Police, looks at a pile of around 4,500 prohibited firearms that have been handed in over the past month under the Australian government's buy-back scheme in Sydney, Australia, July 28, 2017.David Gray/File photo

SYDNEY (Reuters) - Australia said on Friday it would introduce a three-month national gun amnesty, the first in more than 20 years, in a bid to reduced the number of illegal firearms which have been used in recent Islamist-inspired attacks.

Australian Justice Minister Michael Keenan said that from July 1, locals can hand-in illegal firearms to authorities without prosecution.

"We are living in a time when our national security environment has deteriorated. Unfortunately, we have seen, through terror attacks in Australia that illegal guns have been used," said Keenan.

Australia's has some of the world's toughest gun control laws, introduced after the country's worst mass murder, when a gunman killed 35 people at Port Arthur in the island state of Tasmania in 1996.

Australia, which has banned all semi-automatic rifles and all semi-automatic and pump-action shotguns, and as a restrictive system of licensing and ownership controls, has had no mass shootings since 1996. It is held up by many abroad as an example of the need for tighter gun controls in the United States..

But a 2016 report estimated there were 260,000 illegal firearms in Australia, some of which have been used by radicalized locals to commit attacks.

In Australia's most deadly incident inspired by the Islamic State group, a gunman used an illegal firearm in a 2014 Sydney cafe siege in which three people, including the hostage taker, were killed.

Earlier this month, gunman Yacqub Khayre used an illegal firearm to kill a man in an apartment block in Melbourne and then held a woman hostage before police shot him dead. The attack was claimed by Islamic State and classified as "an act of terrorism" by Australian Prime Minister Malcolm Turnbull.